1. Field of the Invention
The present invention relates to an internal combustion engine.
2. Description of the Related Art
In a known engine in which fuel is directly injected into the cylinder of the engine, a depression is formed on the top face of the piston, fuel is injected from the fuel injector toward the depression, a swirl motion, swirling about the axis of the cylinder, is created in the combustion chamber, and an ignitable air-fuel mixture is formed around the spark plug due to the swirl motion (see Japanese Unexamined Utility Model application No. 1-124042).
In this engine, however, such a swirl motion swirling about the axis of the cylinder must be created, and therefore, where such a swirl motion can not be created, the method of forming the air-fuel mixture around the spark plug by using the swirl motion can no longer be adopted. Further, in this engine, the strength of the swirl motion is changed in accordance with a change of the operating state of the engine. Therefore, if the formation of the air-fuel mixture around the spark plug relies completely on the swirl motion, a problem arises in that it is difficult to create a proper air-fuel mixture around the spark plug for all of the operating states of the engine.